About 40,000 years ago in what we now call Italy and the Caucasus Mountains, which straddle Europe and Asia, several volcanoes erupted in quick succession, according to a new study .

After analysing pollen and ash from the affected area, researchers concluded that the eruptions might have reduced or wiped out local bands of Neanderthals and indirectly affected farther-flung populations.

Varying concentrations of pollen found in key sediment layers in Russia's Mezmaiskaya Cave, correlated with patterns in ancient ash layers in the region, suggest that plant populations crashed after the volcanic eruptions, says the study.

The researchers examined sediments layer from around 40,000 years ago in Russia's Mezmaiskaya Cave and found that the more volcanic ash a layer had, the less plant pollen it contained.

"We tested all the layers for this volcanic ash signature. The most volcanic-ash-rich layer"-likely corresponding to the so-called Campanian Ignimbrite eruption, which occurred near Naples (map)-"had no [tree] pollen and very little pollen from other types of plants. It's just a sterile layer," National Geographic News quoted Cleghorn as saying.

The loss of plants would have led to a decline in plant-eating mammals, which in turn would have affected the Neanderthals, who hunted large mammals for food.

"This idea of an environmental cause for the Neanderthals' demise has been out in the literature. What we're trying to do is point out a specific mechanism," said study team member Naomi Cleghorn, an anthropologist at the University of Texas, Arlington.

Other theories propose that modern humans played a vital role in the fall of the Neanderthals, either through competition, warfare, or interbreeding.

If the volcanoes theory is correct, the Neanderthals' end was much more tragic-dying slowly in a cold and desolate landscape bereft of food sources.

"It's hard to say what it would have been like to be the last few groups out there, seeing other groups less and less over the years," said Cleghorn.

The eruptions 40,000 years ago were unlike anything Neanderthals had faced before, said the researchers.

For one thing, all the volcanoes apparently erupted around the same time. And one of those blasts, the Campanian Ignimbrite, is thought to have been the most powerful eruption in Europe in the last 200,000 years.

There may also have been small bands of Homo sapiens living in Europe at the time, said Cleghorn. They too would have been affected by the eruptions.

But modern humans likely avoided extinction because they had larger populations in Africa and Asia, she said, while most Neanderthals were in Europe around this time.

"With their small population groups, Neanderthals did not really have a great source population. They didn't really have the numbers and the density" to rebuild their populations after the eruptions," said Cleghorn.

The study is published in the October issue of the journal Current Anthropology. (ANI)